This invention relates to a process for detecting the completion of a sterilizing treatment using a color changing indicator composition, in case medical and surgical instruments are sterilized with an alkylene oxide, particularly with gaseous ethylene oxide.
Medical materials such as gauzes, bandages, or absorbent cotton, or surgical instruments such as injectors, scalpels, or scissors have hitherto been used after they have been sterilized with dry heat, pressure steam, or by boiling, using a sterilizer in the hospital. However, they have recently been supplied to users (such as hospitals and medical practioners) in a hermetically sealed sterilized style after they have been completely sterilized in the factory of the manufacturer for medical and surgical materials, instead of sterilizing them immediately prior to their use in hospitals or the like. Gaseous sterilization is most suitable for carrying out such sterilizing treatment, and gaseous ethylene oxide is used for this purpose.
This process depends on an improvement of a hermetically sealing material which permits a germ-free state of the hermetical sealing to be maintained after it has been sterilized. Hermetically sealed materials are completely sterilized in the manufacturer's factory on a large scale and supplied to users thereafer, so they may serve for use immediately after they are taken out of the package as they are required. For such hermetically sealed condition, a detection of the completion of the sterilization should, needless to say, be necessary.
As conventional indicator compounds which change in color by the action of gaseous ethylene oxide, such reagents that contain a hydrochloric acid salt of a basic substance together with a pH indicator have generally been used hitherto. The hydrochoric acid salt of the basic substance is reacted with ethylene oxide, to remove the hydrochloric acid. The thus remaining basic substance acts with pH indicator to cause the color change. However, the constancy of such color change is not satisfactory to detect the completion of the sterilizing treatment with accuracy, because the color change may also be caused by contact with a slightly acidic or basic substance in the atmosphere.
Further, indicator compounds having particular characteristics are also known, e.g. compounds having a pyridine ring as represented by 4-(4-nitrobenzyl)pyridine, etc. Such compounds change in color from white to pale blue by a reaction with gaseous ethylene oxide in the presence of an alkaline catalyst. But the extent of the color change, namely, the hue and the strength before and after the gaseous sterilization, are both unsatisfactory and are not suitable for detecting the completion of the sterilization with naked eyes.
The primary object of this invention is to provide a process for detecting the sterilized effect with the naked eye using an indicator composition therefore which changes color distinctly when said sterilization is performed with gaseous ethylene oxide and is stable for atmospheric changes.
Another object of this invention is to provide a process for detecting the sterilized effect of a color changing indicator composition coated or printed on a sealing material used for hermetically sealed medical or surgical materials or instruments with the naked eye by a distinct color change of said composition when said indicator composition is subjected to sterilization together with the instrument with gaseous ethylene oxide.
Other objects and advantages of this invention will clearly be understood from the following description.